Some study of physics desirable--Sound and vibrations--The sounding body--Experiments to illustrate the principles of sound--Qualities of sound--Animals and perception of sound--The range of hearing in man--The larynx as a musical instrument--Experiments of Johannes Mueller--Discovery of the laryngoscope by Garcia--Description of the instrument--Method of using the laryngoscope--The difficulties--Auto-laryngoscopy--The importance of both laryngoscopy and auto-laryngoscopy--Change in size of the larynx due to use--Delicate changes in the laryngeal mechanism--Changes in the larynx during adolescence--Warnings--The "breaking" of the voice--Analogies with fatigue, etc.--When should singing be begun?--Singing with others--Choral singing 97 CHAPTER VIII. FURTHER CONSIDERATION OF BREATHING, LARYNGEAL ADJUSTMENT, ETC. Various kinds of breathing, as "abdominal," "clavicular," etc., discussed--Control of the whole of the breathing mechanism urged--Correct breathing as a habit--Breathing in the most vigorous speaking and singing--Different views expressed by a diagram--Economy of energy in art--Reserve energy in breathing--"Pumping"--_Coup de glotte_--"Attack"--Breath-adjustment--Quality of sound the prime consideration in tone-production--Tremolo and other faults--Tests of good breathing--Mouth-breathing--Exercises--Singing of a single tone--Its relation to scale-singing--Summary and review 118 CHAPTER IX. THE RESONANCE-CHAMBERS. Vocal bands and resonance-chambers compared--Improvised mechanism to illustrate resonance--Musical instruments as resonance-bodies--A vowel in relation to the resonance-chambers--Description of the resonance-chambers--How the quality of tones may be made to vary--New views as to the sounding-chambers--Summary 140 CHAPTER X. THE REGISTERS OF THE SINGING VOICE. A controverted subject--Definitions of a register--Qualifications for dealing with this subject--Madame Seiler--Tabular statement of her views--Garcia's and Behnke's divisions of registers--Sir Morell Mackenzie's views in detail--The author's earlier investigations--Madame Marchesi's views and practice 151 CHAPTER XI. FURTHER CONSIDERATION OF THE REGISTERS OF THE SINGING VOICE.